The Jandd helmet cover will fit most bike helmets and keep water from penetrating. Made with 200 Nylon Oxford with a laminated urethane layer. All Seams are heat sealed and sew holes are covered. 3M Reflective Tape is sewn to the front and back, additionally the back has a loop for a high visibility flashing light. We also have a larger size for the few helmets that this cover will not fit.